Conducting fluid inertia type switch with linearly movable conductive plunger contact

ABSTRACT

A switch which is closed or opened by an external force applied thereto. A weight resiliently suspended in the switch casing and an electrically conductive liquid in the casing are alternatively caused by an external force applied thereto to move thereby to establish electrical connection between the two switch terminals.

United States Patent 1 Tomohiro et al.

[ 1 3,740,503 1 June 19, 1973 Filed: May 8, 1972 Appl. No.: 250,965

US. Cl ZOO/61.4.7, ZOO/61.53, 200/210 Int. Cl. H0lh 35/02, HOlh 29/16 Field of Search ZOO/61.47, 61.51,

. ZOO/61.52, 209, 210

References Cited UNITED STATES PATENTS 2,291,236 7/1942 Kilgour ZOO/61.47

Brutscher, Sr. et al.....r ZOO/61.47 X

3,001,039 9/1961 Johnson ZOO/61.51 X 3,128,358 4/1964 Mitchell et al Mordaunt et al. 200/209 X Primary Examiner-J. R. Scott Att0rneyChristensen & Sanborn [57] ABSTRACT A switch which is closed or opened by an external force applied thereto. A weight resiliently suspended in the switch casing and an electrically conductive liquid in the casing are alternatively caused by an external force applied thereto to move thereby to establish electrical connection between the two switch terminals.

12 Claims, 10 Drawing Figures Patented June 19, I973 3,?4Q503 4 Sheets-Sheet :5

' I Patented June, 19, i13 3,140,503-

4 shuts-sheet CONDUCTING FLUID INERTIA TYPE SWITCH WITH LINEARLY MOVABLE CONDUCTIVE PLUNGER CONTACT ever, in any of them, it is the force applied in a singlev predetermined direction alone that enables their operation. For example, one prior art switch is so designed as to operate only when a horizontal force is applied thereto. The switch can not be operated by a vertical force applied thereto. At least two such switches are required in order to be able to operate in response to both vertical and horizontal .forces.

The primary object of the invention is therefore to provide a switch operable in response to a force externally applied thereto regardless of the direction in I which the force is applied.

Another object of the invention is to provide a switch which can exactly operate in response "to both horizontal and vertical forces.

Another object'of the invention is to provide a switch which operates when the force applied thereto exceeds a predetermined magnitude, regardless of the direction in which the force is applied.

.Anotherobject of the invention is to provide a switch in which it is possible to selectively determine the mag nitude of the force that effects operation of the switch.

.Still another object of the invention isto provide" an apparatus which comprises such a switch as aforesaid and a circuit operable in response to the operation of the switch to provide an outputto be appliedto a load,

the switch and the circuit'being enclosed in a single housing.

Still -anotherobjectof the invention is to provide such an apparatus as aforesaid in which the output fromsaid circuit continues a predetermined period of time.

The switch of the invention chiefly comprises a hollow cylindrical casing made of an electrically insulating material such as glass and containing an electrically conductive "'liquid material such as mercury and a bore of the weight, so that the resiliency of the spring urges the weight downwardly. One end of the lower coil spring is secured to the lower terminal member and the other end thereof isborne against a contact disk provided in the axial through bore of the weight, so that the resiliency of the spring urges the weight upwardly. The resiliency of the upper spring and the mass of the weight balances the resiliency of the lower spring so that the weight is held in suspension inside the casing.

The switch is held in a vertical position with the axes of the terminal members in vertical alignment with 1 each other and secured to a suitable support. Under the condition, the weight remains stationary. Suppose that a force or impact is applied to the switch in the horizontal direction. The weight more or less swings in the horizontal direction but is never moved in the vertical direction. However, the conductive liquid in the casing produces a reactive force against the horizontal force. This reactive forcecauses the liquid to move inside the casing, so that the surface of the liquid which was horizontal underthe normal condition now becomes in clined or aslant. The angle of this inclination is proportional to the magnitude of the force that has been applied. When the force exceeds a predetermined magnitude and the inclination of the liquid surface exceeds a predetermined angle, the liquid-surface contacts a lower portion of the weight, thereby establishing an electrical connection between the weight and the liquid. 'As previously described, the upper coil spring is in contact with the weight and the lower coil spring, with the liquid and the two coil springs, with the upper and lower terminal members, respectively, so that the two terminal members have now been electrically connected. This means that the switch has now been closed. A moment after the liquid surface is restored to its original horizontal level, whereupon the contact between the weight and the liquid is broken, so that the held'inside the casing, the vertical force causes the weightof an electrically conductivematerial resiliently suspended in the space of the casing. Normally, the weight is held aboveand out of contact with the surface of the conductiveliquid. However, the weight is resiliently held there so that it is vertically movable relative to the surface of the conductiveliquid. A pair of tubular terminal? members are secured to theupper and lower sides of the casing. Each terminal member serves as a guide for the weight as the latter moves vertically inside the casing,'and also asa pipe through which the inside space of the casing is evacuated. After evacuation the opening of each tubular terminal member is tightly closed by crushing a part of the tube. The weight is formed with an axial through bore, into the opposite ends of'which the two terminal members are inserted as far as the inner ends thereof are positioned in the bore with a predetermined gap therebetween.

In order to resiliently support theweight inside the casing, a coil spring is provided encircling each of the terminal members. One end of the upper coil spring is secured totheupper terminal member while the other end is borne against the inner surface of the through weight to be moved in the opposite direction to that of the force. If the weightis moved downwardly, it comes into contact with the-liquid. On the contrary, if it is 'moved upw ardly, the contact disk inside the axial bore of the weight comes into contact with the lower end of the upper terminal member. Since the lower coil spring is always in contact with thecontact disk, the upper and lower terminal members are thus electrically connected, so that the switch is closed. At the next moment the weight is restored to the original position, thereby opening the switch.

When vibration is applied to the switch, the same operation as mentioned above is effected regardless of the direction in which the vibration occurs.

It is understood from the above description that the switch is instantaneously closed upon application of an external force thereto and a moment thereafter it is again opened. Therefore, if it is required to continuously supply electric energy to a load through the switch, the above arrangement of the switch is not sufficient. To meet the requirement, the signal obtained upon closure of the switch may be used to actuate a different circuit to produce a continuous output to be suppliedto the load. As such a circuit a monostable circuit may be used A bistable circuit may also serve the purpose if a reset signal is provided by a different suitable circuit. Preferably, such a circuit is provided in the form of a printed circuit having necessary circuit elements such as transistors, resistors, etc. printed on a base. The printed circuit together with the switch may conventently be enclosed in a single casing.

The invention will be described in further detail with reference to the accompanying drawings wherein;

FIG. 1 is a vertical section of a preferred embodiment of the invention, the switch being shown in its normal, open condition;

FIG. 2 is a view similar to FIG. 1 but showing the switch in a transient, closed condition as a horizontal force is applied thereto from the right-hand side in the figure;

FIG. 3 is a view similar to FIG. 1 but showing the switch in a transient, closed condition as a vertically downward force is applied thereto;

FIG. 4 is a view similar to FIG. 1 but showing the switch in a transient, closed condition as a vertically upward force is applied thereto;

. FIG. 5 is a verticalsection of an apparatus comprising the switch and a circuit to be actuated thereby enclosed in a single casing;

FIG. 6 is a top plan view of FIG. 5, with the casing partially cut away to 'show the interior elements;

FIG. 7 is a diagramof the circuit used in FIGS. 5 and FIG. 8 is a waveform diagram to explain the operation of the circuit of FIG. 7;

FIG.' 9 is a diagram .of another form of the circuit used in FIGS. 5 and 6; and FIG. 10 is a waveform diagram to explain the operation of the circuit of FIG. 9.

In FIG. 1 there is shown a generally cylindrical casing 10 madeof electricallyinsulating transparent glass. A pair of terminal members 11 and 12pierce through the upper and lower end walls of the casing 10, respectively, to be fluid-tightly secured thereto in axial alignment with each other and the axis of the casing. Each terminal member comprises a tube of an electrically conductive material with its opposite ends initially open. Inside the casing there is provided a weight 14 made of an electrically conductive material and having an axial through bore 15. The weight is resiliently suspended in the casing 10 so that the bore 15 is aligned with the axis of the casing, as will be described later in detail. The'inner end portions of the terminals 11 and 12 are inserted into the opposite ends of the through bore 15 of the weight 14 so that a gap is provided between the opposing ends of the terminals inside the bore 15. The portion of each terminal projecting outw side'the casing 10 is used for electrical connection to an external circuit.

Spirally encircling the upper terminal 11 inside the casing 10 there is provided a coil spring 16 made of an electrically conductive material. The spring has its upper end held in contact with the upper terminal member 11 and its lower end borne against a shoulder 24 formed in the through bore 15 of the weight so that the spring resiliently biases the weight downwardly. In this manner an electrical connection is established between the upper terminal 11 and the weight 14 through the coil spring 16. In a similar manner, a lower coil spring 18 spirally encircles the lower terminal member 12 inside the casing 10. The spring 18 has its lower end held in contact with the lower terminal 12 and its upper end borne against a contact disk 20 secured in the through bore 15 of the weight 14 axially spaced from the shoulder 24, so that the spring 18 resiliently biases the weight upwardly. Thus, the mass of the weight and the resiliency of the upper spring l6'balances the resiliency of the lower spring 18 thereby to hold the weight in suspension.

The contact disk 20 is electrically separated from the weight by means of an insulating sleeve 22 inserted into the lower half of the through bore 15. This sleeve also electrically separates the lower coil spring 18 and the lower terminal 12 from the weight. The disk 20 need not be mechanically fixed to the sleeve but may simply be placed on a shoulder 23 formed in the upper end of the sleeve since the lower coil spring holds the disk there. A tiny hole 21 may advantageously be formed in the disk 20 to decrease the fluid resistivity thereof upon vertical movement of the weight, as will be described later.

Inside the casing 10 there is contained a predetermined amount of electrically conductive liquid 26 such as mercury and also preferably hydrogen gas to improve the fluidity of themercury. The mercury is always in contact with the lower coil spring 18.

In the actual manufacturing process of the switch of the design shown and described, it is advisable to initially produce two halves of the casing formed by dividing the casing by a plane perpendicular to the axis thereof and fix the necessary parts and elements to each of the halves and then put them together into a complete casing, with the weight held in suspension therein as previously described. One of the tubular terminal members, say, 11 is then closed, and through the other terminal opening the casing is evacuated, and mercury and hydrogen are introduced into the casing and then the opening of this tubular terminal 12 is closed. The amount of hydrogen is preferably such as to keep the inside pressure twice atmosphere.

The switch is secured to a suitable frame or base in the vertical position as shown in FIG. 1. The base with the switch thereon is put on a place where external forces are applied to the switch.

Suppose that as shown in FIG. 2 an external force has been applied to the switch form right to left in the horizontal direction of an arrow 31. Despite the shock, the

casing 10 is not moved in the direction since it is fixed to the base. Nor is the weight vertically displaced by the horizontal force since the weight is movable only vertically. However, since the mercury 26 in the casing is free to move, the force applied causes the mercury to move so that the right-hand portion of the mercury rises, that is to say, the surface thereof is inclined upwardly to the right relative to the horizontal line, as shown in FIG. 2. The angle of inclination is proportional to the magnitude of the force applied.

Suppose that a sufficient force has been applied to cause the level of the mercury to be sufficiently inclined to touch the lower right-hand corner of the weight 14. An electrical connection is then established between the upper and lower terminals through the upper coil spring 16, the weight 14 and the mercury 26. In other words, the switch has now been closed. A moment after, the mercury is displaced in the opposite direction to decrease the angle of inclination of the surface and then again in the direction to increase the angle of inclination. At this time, however, the surface does not rise as high as the previous level. The surface swings in this manner till it is returned to the original horizontal level after a short time.

If a force is applied to the switch in the opposite direction to the arrow 31, that is horizontally from the left-hand side, or perpendicular to the plane of the drawing sheet, the same operation as mentioned above is effected to close the switch except that the direction of inclination of the surface of the mercury differs de- 7 other words, in order to determine the magnitude of I the force required, the amount of mercuryand the nor- 7 mal position of the weight may accordingly be determined.

The periphery of the lower end of the weight may be tapered as at 28, so that by changing the angle of the v tapered edge 28 it is possible to vary the magnitude of the force required to cause the surface of the mercury to be inclined into contact with the tapered edge of the weight. I

Now turning to FIG. 3, suppose that a force has been applied to the switch in the direction on an arrow 32, that is, vertically downwardly. The weight 14 is instantaneously moved downwardly to compress the lower coil spring 18. At the next moment the resilient energy stored in the coil spring 18 causes the weight to move upward as far as the contact disk 20 moving together with the weight comes into contact with the lower end of the upper terminal 11 as shown in FIG. 3, whereupon the upper and lower terminals 11 and 12 are electrically connected through the contact disk 20, the spring 18 and the mercury 26. This means that the switch has now been closed. After a moment the weight .-moves downward and then again upward. The vertical reciprocal movement or vibration continues with the amplitude decreasing until the weight comes to a standstill at the position of FIG. 1.

tween the upper and'lower terminals 11 and 12 through the upper coil spring 16, the weight 14 and the mercury 26. This means that the switch has now been closed. In this case, too, it is possible to set the force required for operation of the switch to a desired magnitude by appropriately selecting the amount of the mercury 26, the mass of the weight 14 and the resiliency of the springs 16 and 18.

In the above explanation, the force is applied to the switch in the form of a shock or impact. The same course of events occurs if it is applied in the form of vibration and also if the casing 10 is tilted instead of a force being applied thereto.

As can be understood from the above description, the switch of this invention is closed upon application of a force thereto and a moment after that it is again opened. Therefore, in order to continue power supply to a load for a certain period of time, some other circuit is required, which may advantageously be a monostable circuit. Practically it is convenient to have such a circuit and the switch together enclosed in a single housing so as to be dealt with as a single device. FIG. 5 shows an example of such an arrangement. A housing 41 made of a suitable synthetic resin encloses the switch of FIG. I designated here by 1 and such a monostable circuit as mentioned above in the form of a printed circuit. The casing 10 of the switch is preferably enclosed in a protectivecover 43 made of, preferably, a shrinkable plastic tube. The housing 41 has a base 44, which is fixed by means of screws to a member to which external forces are applied. The switch 1 is placed on a base 45 and secured to the housing 41, with the peripheral wall of the casing 10 of the switch 1 in contact with the adjacent two walls of the housing 41,

so that the force applied to the housing is directly transmitted to the switch 1. Leads 60 connects the terminals 11 and 12 to the printed circuit, which comprises a base 42 and a monostable circuit printed thereon. The

circuit comprizes transistors 47, a condenser 48, resistors 49, etc. If necessary, a heat-radiating plate 50 is additionally provided, which supports a transistor 51 and other necessary elements.

The monostible circuit'may be of any provided that when the switch is closed the circuit produces an output continuing for a predetermined period of time. Examples of the monostable circuit are illustrated in FIGS. 7 and 9. In FIG. 7 a monostable circuit chiefly comprises a pair of transistors 71 and 72, a

, resistor 73 and a condenser 74 for deteermining the time constant of the circuit. The switch 1 is connected across the transistor 72. A load 76 is connected to a switchingtransistor 75. With a voltage B being applied to source terminal 77, the transistor 71 is on and the transistor 72, of and the transistor 75, of so that no power is supplied to the load 76. The circuit is at this time in the stable condition. The condenser 74, however, is'charged with the base current of the transistor 71 to the level E at the polarity shown in FIG. 7.

Under the condition, when the switch 1 is closed, an inverted input is applied between the emitter and collector of the transistor 72, so that the potential at pont A becomes E as shown in FIG. 8a. As a result, the transistor 75 is turned on and the resulting amplified current flows through the load 76. On the other hand, the instant the switch 1 has been closed, the condenser 74 is short-circuited, so that the potential at point B transiently becomes about 2E as shown in FIG. 8b. As a result, the transistor 71 is counter-biased between the base and the emitter thereof, so that the transistor 71 is turned off. The moment the switch is again opened, a base current flows through the transistor 72, which is then turned on, so that the condenser 74 is continuously discharged through the resistor 73 until the opotential at B decreases to a level enough to turn on the transistor 71.

During this course of events the operative conditions of the transistors 71, 72 and 75 are kept as they are, so that the output of the transistor 75 is continuously apsuitable design plied to the load 76 for a period of time t. The time t is determined by the time constant of a delay circuit composed of the condenser 74 and the resistor 73.

As the condenser 74 is discharged, the potential at point B is reduced to the operating voltage level E of the transistor 71, whereupon a current flows through the base'of the transistor 71 to restore it to the on condition. Then the condenser 74 is beginning to be charged again. Simultaneously, the transistors 72 and 75 are turned off again, so that the power supply to the load 76 is stopped. The whole circuit has now been restored to its original condition.

The arrangement of FIG. 7 is such that normally no current is supplied to the load and when the switch is closed, the current supply is started. In FIG. 9, however, normally current is supplied to the load and when the switch is closed the current supply is stopped for a predetermined period of time. Here, the switchl is connected between the base and emitter'of the transistor 72.

Witha' voltage E impressed on the source terminals lector current of-the transistor 72. Of course the switch is kept opened at this time.

Under the condition, when the switch is closed, an inverted input is applied to the transistor 72 between the base and emitter thereof, so that the voltage at point A is reduced to zero as shown in FIG. 10a. As a result, the potential at point B becomes lower by E-volt than the potential at A as shown in FIG. 10b, so that the transistor 71 is turned off. On the other hand, due to the potential at A having become 0 volt, the transistor 75 also is turned off, so that the current supply to the load 76 is stopped.

After a moment the switch 1 is opened, but the potential at Bis 'kept negative, so that the then operative conditions of the transistors 71, 72 and 75 remain unchanged. During the course of events, the condenser 74 is continuously discharged through the resistor 73.

. constant of the delay circuit consisting of the condenser 74 and the resistor 73.

A bistable circuit may be used instead of the monostable circuit, provided that a reset signal is provided by means of a different circuit.

Such an arrangement is obvious to those skilled in the art so that no description thereof will be necessary.

What we claim is:

1. A switch comprising: a casing made of an electrically insulating material; a weight made of an electrically conductive material and resiliently suspendedinside said casing so to be displaceable along the axis of said casing; electrically conductive liquid enclosed inside said casing to lie at the bottom thereof; a first terminal member secured to said casing and electrically connected to said weight; a second terminal member secured to said casing and having a portion thereof disposed in contact with said liquid; and a contact member provided on said weight but electrically separated therefrom and disposed in contact with said second terminal member; whereby when an external force is applied to said casing, said weightjs displaced axially of said casing, and alternatively said liquid is displaced to cause its surface to become inclined, as far as said weight comes into contact with said liquid and alternatively said contact member comes into contact with said first terminal member, thereby establishing an electrical connection between said first and second terminal members.

2. The switch of claim 1, wherein said weight is formed with an axial through bore so that the inner ends of said terminal members are inserted into the opposite sides of said axial bore with a gap therebetween, said contact member being disposed in said gap.

3. The switch of claim 2, wherein said contactmember is formed with a hole to reduce the fluid resistivity of said contact member as the same is moved together with said weight.

4. The switch of claim 1, wherein said first terminal member is provided with a coil spring spirally encircling at least a portion of said first terminal member and having one end thereof in contact with said first terminal member and the other end in contact with said weight, thereby electrically connecting said first terminal member to said weight and resiliently supporting said weight.

5. The switch of claim 1, wherein said second terminal member is provided with a second coil spring spirally encircling at least a portion of said second terminal member so as to resiliently support said weight through said contact member.

6. The switch of claim 1, wherein each of said first and second terminal members is provided with a spirally encircling coil spring one end portion of which is positioned in said weight through bore so as to resiliently support said weight.

7. The switch of claim 1, wherein said weight is provided with a tapered surface to be brought into contact with the surface of said liquid as said liquid surface is inclined.

8. The switch of claim 1, wherein at least one of said terminal members is tubular so that evacuation of said casing and introduction of said liquid into said casing may be effected through said tubular terminal member.

9. In combination with the switch of claim 1, an electrical circuit so designed as to be operable upon establishment of electrical connection between said first and second terminal members to produce an output which continues for a predetermined period of time.

10. The combination of claim 9, further including a housing enclosing said switch and said circuit so that when an external force. is applied to said housing, said force is transmitted from said housing to said switch casing.

11. The combination of claim 9, wherein said circuit is a monostable circuit.

'12. The combination of claim 10, wherein said circuit is a monostable circuit. 

1. A switch comprising: a casing made of an electrically insulating material; a weight made of an electrically conductive material and resiliently suspended inside said casing so to be displaceable along the axis of said casing; electrically conductive liquid enclosed inside said casing to lie at the bottom thereof; a first terminal member secured to said casing and electrically connected to said weight; a second terminal member secured to said casing and having a portion thereof disposed in contact with said liquid; and a contact member provided on said weight but electrically separated therefrom and disposed in contact with said second terminal member; whereby when an external force is applied to said casing, said weight is displaced axially of said casing, and alternatively said liquid is displaced to cause its surface to become inclined, as far as said weight comes into contact with said liquid and alternatively said contact member comes into contact with said first terminal member, thereby establishing an electrical connection between said first and second terminal members.
 2. The switch of claim 1, wherein said weight is formed with an axial through bore so that the inner ends of said terminal members are inserted into the opposite sides of said axial bore with a gap therebetween, said contact member being disposed in said gap.
 3. The switch of claim 2, wherein said contact member is formed with a hole to reduce the fluid resistivity of said contact member as the same is moved together with said weight.
 4. The switch of claim 1, wherein said first terminal member is provided with a coil spring spirally encircling at least a portion of said first terminal member and having one end thereof in contact with said first terminal member and the other end in contact with said weight, thereby electrically connecting said first terminal member to said weight and resiliently supporting said weight.
 5. The switch of claim 1, wherein said second terminal member is provided with a second coil spring spirally encircling at least a portion of said second terminal member so as to resiliently support said weight through said contact member.
 6. The switch of claim 1, wherein each of said first and second terminal members is provided with a spirally encircling coil spring one end portion of which is positioned in said weight through bore so as to resiliently support said weight.
 7. The switch of claim 1, wherein said weight is provided with a tapered surface to be brought into contact with the surface of said liquid as said liquid surface is inclined.
 8. The switch of claim 1, wherein at least one of said terminal members is tubular so that evacuation of said casing and introduction of said liquid into said casing may be effected through said tubular terminal member.
 9. In combination with the switch of claim 1, an electrical circuit so Designed as to be operable upon establishment of electrical connection between said first and second terminal members to produce an output which continues for a predetermined period of time.
 10. The combination of claim 9, further including a housing enclosing said switch and said circuit so that when an external force is applied to said housing, said force is transmitted from said housing to said switch casing.
 11. The combination of claim 9, wherein said circuit is a monostable circuit.
 12. The combination of claim 10, wherein said circuit is a monostable circuit. 